Long reach optical network

ABSTRACT

An optical network includes a first optical network for carrying a plurality of optical channels in an optical fiber, wherein each of the plurality of optical channels comprise a discrete wavelength in a first range of wavelengths. A second optical network coupled to the first optical network by a first tunable filter. A first customer location coupled to the second optical network by a second tunable filter. The first tunable filter is configured to pass a first set of optical channels from the first optical network to the second optical network. The first set of optical channels includes a subset of the plurality optical channels within a second range of wavelengths less than the first range of wavelengths. The second tunable filter is configured to pass a particular channel within the first set of optical channels from the second optical network to the first customer location.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/611,008 filed Dec. 14, 2006, the entirety of which is herebyincorporated by reference herein.

BACKGROUND

With the explosion in communication via the Internet in recent years,there has been a corresponding increase in demand for high bandwidthnetworks, such as networks incorporating optical fibers. One type ofnetwork architecture includes several different classes or types ofnetworks coupled together to enable users to communicate with eachother. Enterprise or access level networks provide bandwidth toindividual customers and typically connect to larger metropolitan levelnetworks. The metropolitan level networks, in turn, typically connect toeven larger long haul or backbone level networks. In one type of networktopology, each network is configured as a ring, with each ring having anumber of nodes configured to add or drop traffic to or from the parentnetwork.

In conventional metropolitan level ring networks (often referred to asmetropolitan area networks or MANs), carrier level switching facilitiesreceive traffic from the long haul network and distribute the trafficamong a number of carrier aggregation facilities using SynchronousOptical Network/Synchronous Digital Hierarchy (SONET/SDH) framesdelivered via time domain multiplexing (TDM) technologies. Eachaggregation facility connects to an access level network for deliveringthe SONET/SDH frames to customer premises.

Unfortunately, TDM aggregation and processing equipment is costly anddifficult to maintain. Each aggregation point on a traditional SONETover TDM network requires significant infrastructure development.Additionally, switching systems associated with SONET frames deliveredvia TDM require costly traffic grooming and other equipment at theenterprise or local network level. Lastly, the optical-to-digital anddigital-to-optical conversions required to process TDM signals introduceadditional cost and potential errors at the aggregation facilities andcustomer premises locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate an implementation of theinvention and, together with the description, explain the invention. Inthe drawings,

FIG. 1 is a block diagram illustrating an exemplary communicationssystem 100 in which systems and methods described herein may beimplemented;

FIG. 2 is another block diagram illustrating an exemplary communicationssystem 200 in which systems and methods described herein may beimplemented; and

FIG. 3 is a block diagram illustrating one exemplary configuration of acustomer premises connection to an access network as depicted in FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description of implementations consistent withthe present invention refers to the accompanying drawings. The samereference numbers in different drawings may identify the same or similarelements. Also, the following detailed description does not limit theinvention. Instead, the scope of the invention is defined by theappended claims and equivalents.

Systems and methods described herein provide cost-effective deploymentof metropolitan to enterprise access level optical networks. In oneimplementation, a first set of tunable optical filters may be used todirect ranges or bands of long reach wavelength division multiplexing(WDM) channels through a metropolitan network to a number of enterpriselevel access networks. A second set of tunable optical filters locatedon each access network may be used to direct individual WDM channels tocustomer premises locations.

FIG. 1 is a block diagram illustrating an exemplary communicationssystem 100 in which systems and methods described herein may beimplemented. Communications system 100 may include multiple networksincluding a long haul network 102, a metropolitan (“metro”) ring network104, and a number of enterprise access (“access) rings 106. Metro ring104 may be coupled to long haul network 102 at a carrier switch facility108. Access rings 106 may be coupled to metro ring 104 at a number ofnodes 110. A number of customer premise locations 112 may be coupled toeach access ring 106.

Traffic to and from high bandwidth long haul network 102 may be switchedon to and off of metro ring 104 by carrier switch 108. Traffic on metroring 104 may be further directed to access rings 106 at each node 110.The traffic may then be routed or delivered from the access rings 106 torespective customer premises locations 112. As will be described inadditional detail below, systems described herein may enable efficientand low cost delivery of optical signals from carrier switch 108 tocustomer premises locations 112 without requiring expensive aggregationor optical to digital conversions.

FIG. 2 is a block diagram illustrating one exemplary communicationssystem 200 implementation of a metro ring and access ring configuration.System 200 may include a metro ring 204, a number of access rings 206 a,206 b, and 206 c, and a number of customer premises locations 208 a, 208b, 208 c, 208 d, and 208 e. As illustrated, metro ring 204 may becoupled to long haul networks 202 a and 202 b by a carrier switchingfacility 210. Additionally, access rings 206 a-206 c may be coupled tometro ring 204 by a number of banded optical filters 212 a, 212 b, and212 c, respectively. Customer premises locations 208 a-208 e may becoupled to access rings 206 a-206 c by a number of channelized opticalfilters 214 a, 214 b, 214 c, 214 d, and 314 e.

In an exemplary implementation, switching facility 210 may providetraffic to and from long haul network 202 to metro ring 204 usingwavelength division multiplexing (WDM) technologies. As is known, WDM isa more recent optical transmission technology that enables a number ofdiscrete optical wavelengths to be multiplexed or simultaneouslytransmitted on a single optical fiber. A variant of WDM known as denseWDM or DWDM enables between 80 and 100 or even more discrete opticalchannels to travel within a single fiber.

In one implementation, carrier switching facility 210 may include anumber of add/drop multiplexers 216 (ADMs) configured to connectswitching equipment to long haul networks 202 a and 202 b or,alternatively, to adjacent metro rings, thereby facilitating thetransfer of traffic between the networks. In one implementation, longhaul networks 202 a and 202 b and/or adjacent metro rings may includeOC-192 four fiber bi-directional line switching rings (BLSR/4F)configured to cover distances as long as 600 kilometers (km). As isknown, OC-192 supports speeds of approximately 10 gigabits per second.Additionally, a BLSF/4F configuration includes a ring topology in whichtwo fibers are provided as working fibers and two fibers are provided asprotection fibers. In one embodiment, ADMs 216 may divide receivedOC-192 signals into four OC-48 signals each capable of speeds up to 2.5gigabits per second.

In one exemplary embodiment, carrier switching facility 210 may alsoinclude a layer 2 IP switch 218 as well as a broadband digital crossconnect (BBDXC) 220 configured to perform multiservice switching betweenlong haul network 202 a or 202 b and metro ring 204. Carrier switchingfacility 210 may include an optical transmitter 222 capable ofmultiplexing and transmitting a number of DWDM channels coveringwavelengths λ₁-λ_(z) over distances of at least about 80 km, where z isan integer representing a last wavelength channel. Unlike conventionaltraffic aggregation and regeneration facilities required by SONET/SDHvia TDM metropolitan networks, traffic forwarded by optical transmitter222 may be capable of reaching customer premises locations 208 a-208 eentirely within the optical domain. In this manner, the aggregationfacilities may be bypassed, resulting in significant cost andmaintenance savings.

Banded optical filters 212 a, 212 b, and 212 c may include tunablepassive filters configured to direct only predetermined DWDM channels tothe associated access rings 206 a, 206 b, and 206 c. For example, asillustrated in FIG. 2, banded optical filter 212 a may be configured topass channels associated with wavelengths λ₁-λ_(i) to access ring 206 a,filter 212 b may be configured to pass channels associated withwavelengths λ_(i+1)-λ_(p) to access ring 206 b, and filter 212 c may beconfigured to pass channels associated with wavelengths λ_(p+1)-λ_(z) toaccess ring 206 c. As described above with respect to variable z,variables i and p are likewise integers representing selected wavelengthchannels along metro ring 204. It should be noted that the number ofaccess rings 206 shown is merely exemplary and that any suitable numberof access rings may be provided, depending on the bandwidth requirementsfor associated customers premises locations 208 a-208 e and the numberof discrete channels transmitted on metro ring 204 by opticaltransmitter 222.

Unlike conventional SONET/SDH via TDM metro rings, by configuring metroring 204 to carry DWDM channels, costly signal aggregation and TDMswitching facilities may be replaced with inexpensive passive filters212 a-212 c.

Channelized optical filters 214 a-214 e may include tunable passivefilters configured to pass only specific channels from access rings 206a-206 c to each respective customer premises location 208 a-208 e. Forexample, one of filters 214 may be configured to pass a single channelto a single customer premises location 208. Alternatively, a filter 214may be configured to pass multiple discrete channels to multiplecustomer premises 208, ensuring that each customer premises 208 receivesa dedicated channel.

As illustrated in FIG. 2, optical filter 214 a may be configured to passchannel associated with a wavelength λ_(i+1) to customer premiseslocation 208 a, optical filter 214 b may be configured to pass a channelassociated with a wavelength λ_(i+2) to a first access point 209 a atcustomer premises location 208 b and a channel associated with awavelength λ_(m) to a second access point 209 b at customer premiseslocation 208 b, optical filter 214 c may be configured to pass a channelassociated with a wavelength λ_(m+1) to customer premises location 208c, optical filter 214 d may be configured to pass a channel associatedwith a wavelength λ_(p−1) to customer premises location 208 d, andoptical filter 214 e may be configured to pass a channel associated witha wavelength λ_(p) to customer premises location 208 e. Variable m is aninteger representing a selected wavelength channel along access ring 206b.

FIG. 3 is a block diagram illustrating one exemplary configuration of anaccess ring 300 and a customer premises location 302. In a mannersimilar to that described above, customer premises location 302 may becoupled to access ring 300 by a channelized filter 304 configured topass a predetermined bandwidth from access ring 300 to a feeder fiber306 associated with customer premises location 302.

A customer premises location initially configured to support SONET/SDHvia TDM (e.g., customer premises location 302) may be served by a singlefiber 306 coupled to access ring 300. This fiber may be referred to as a“feeder fiber”. In a typical configuration, feeder fiber 306 may beincapable of supporting bidirectional traffic of DWDM and WDM channels.In one embodiment described herein, a pair of circulators 308 may becoupled on either ends of feeder fiber 306 to facilitate bidirectionalsupport and enable DWDM traffic to be transmitted both to and fromcustomer premises location 302.

By enabling an all-optical distribution of traffic from a carrierswitching facility to each customer premises location, systemsconsistent with principles described herein may substantially increasethe efficiency of network operations while simultaneously significantlyreducing costs associated with delivering high bandwidth traffic toaccess networks and eventually individual customers.

CONCLUSION

Implementations described herein provide for all-optical delivery ofnetwork traffic through a metropolitan level network, and an accesslevel network to enterprise or customer level locations. In oneimplementation, tunable filters may be used to deliver targetedwavelengths from the metropolitan network to each associated accessnetwork. Additional filters may be used to pass specific trafficchannels from the access networks to customers associated with theaccess networks.

The foregoing description of exemplary embodiments of the presentinvention provides illustration and description, but is not intended tobe exhaustive or to limit the invention to the precise form disclosed.Modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention.

It will be apparent to one of ordinary skill in the art that thefeatures described above, may be implemented in many different forms ofhardware, software, or firmware in the implementations illustrated inthe figures. The actual hardware or control software used to implementthe described features is not limiting of the invention. Thus, theoperation and behavior of these features were described withoutreference to specific hardware or control software—it being understoodthat one of ordinary skill in the art would be able to design hardwareand software to implement the features based on the description herein.

No element, act, or instruction used in the description of the presentapplication should be construed as critical or essential to theinvention unless explicitly described as such. Also, as used herein, thearticle “a” is intended to include one or more items. Where only oneitem is intended, the term “one” or similar language is used. Further,the phrase “based on” is intended to mean “based, at least in part, on”unless explicitly stated otherwise. The scope of the invention isdefined by the claims and their equivalents.

What is claimed is:
 1. An optical network, comprising: a first opticalnetwork for carrying a plurality of optical channels in an opticalfiber, wherein each of the plurality of optical channels comprise adiscrete wavelength in a first range of wavelengths; a second opticalnetwork coupled to the first optical network by a first passive bandedoptical filter; and a first customer location coupled to the secondoptical network by a first tunable filter, wherein the first passivebanded optical filter is configured to pass a first set of opticalchannels from the first optical network to the second optical network,wherein the first set of optical channels comprises a subset of theplurality optical channels within a second contiguous range ofwavelengths less than the first range of wavelengths; and wherein thefirst tunable filter is configured to pass a particular channel withinthe first set of optical channels from the second optical network to thefirst customer location.
 2. The optical network of claim 1, wherein thefirst optical network comprises a metropolitan ring network.
 3. Theoptical network of claim 1, wherein the second optical network comprisesan access ring network.
 4. The optical network of claim 1 furthercomprising: a third optical network coupled to the first optical networkby a second passive banded optical filter, wherein the second passivebanded optical filter is configured to pass a second set of opticalchannels from the first optical network to the third optical network,wherein the second set of optical channels comprises a subset of theplurality optical channels within a third contiguous range ofwavelengths less than the first range of wavelengths and different thanthe second range of wavelengths; and a fourth optical network coupled tothe first optical network by a third passive banded optical filter,wherein the third passive banded optical filter is configured to pass athird set of optical channels from the first optical network to thefourth optical network, and wherein the third set of optical channelscomprises a subset of the plurality optical channels within a fourthrange of wavelengths less than the first range of wavelengths anddifferent than the second range of wavelengths and the third range ofwavelengths.
 5. The optical network of claim 4, wherein the firstoptical network comprises a metro ring, the second optical networkcomprises a first access ring network, the third optical networkcomprises a second access ring network, and the fourth optical networkcomprises a third access ring network.
 6. The optical network of claim1, wherein the first tunable filter comprises a first channelizedoptical filter.
 7. The optical network of claim 6 further comprising: asecond customer location coupled to the second optical network by asecond channelized optical filter, wherein the second channelizedoptical filter is configured to pass a second particular channel withinthe first set of optical channels from the second optical network to thesecond customer location.
 8. The optical network of claim 1 furthercomprising: a second customer location coupled to the second opticalnetwork by the first tunable filter, wherein the first tunable filter isconfigured to pass a first discrete channel to the first customerlocation and a second discrete channel to the second customer location.9. The optical network of claim 1, wherein the first customer locationcomprises an optical access point.
 10. The optical network of claim 1,wherein the first optical network and the second optical networkcomprise dense wavelength division multiplexing (DWDM) networks.
 11. Theoptical network of claim 1, wherein the plurality of optical channelscomprise at least 80 channels.
 12. An optical network comprising: ametro ring network configured to carry traffic in a plurality ofwavelength division multiplexing (WDM) channels; a first access ringnetwork coupled to the metro ring network by a first passive, bandedoptical filter, wherein the first passive, banded optical filter isconfigured to pass a first contiguous subset of the plurality of WDMchannels from the metro ring network to the first access ring network; asecond access ring network coupled to the metro ring network by a secondtunable passive, banded optical filter, wherein the second passive,banded optical filter is configured to pass traffic having a secondcontiguous subset of the plurality of WDM channels from the metro ringnetwork to the second access ring network; and a first customer premiseslocation coupled to the first access ring network by a third firsttunable optical filter, wherein the first tunable optical filter isconfigured to pass traffic on a first discrete channel in the firstcontiguous subset of WDM channels range from the first access ringnetwork to the first customer premises location.
 13. The optical networkof claim 12, wherein the first contiguous subset of WDM channels isdifferent than the second contiguous subset of WDM channels.
 14. Theoptical network of claim 12, wherein each of the plurality of WDMchannels corresponds to a particular wavelength, wherein the firstcontiguous subset of the plurality of WDM channels comprises a firstrange of wavelengths, and wherein the second contiguous subset of theplurality of WDM channels comprises a second range of wavelengthsdifferent than the first range of wavelengths.
 15. The optical networkof claim 14, wherein the first tunable optical filter comprises achannelized optical filter.
 16. A method, comprising: receiving, at afirst node on a metro ring network, an optical signal comprising aplurality of wavelength division multiplexing (WDM) channels, whereinthe first node does not comprise a reconfigurable add/drop multiplexerdevice; filtering, by a first passive, banded filter in the first nodeon the metro ring network, a first contiguous subset of the plurality ofWDM channels; passing, by the first node on the metro ring network, thefirst contiguous subset of the plurality of WDM channels to a firstaccess ring network; receiving the first contiguous subset of theplurality of WDM channels at a second node on the first access ringnetwork; filtering, by a first tunable filter in the second node of thefirst access ring network, a first discrete channel from the firstcontiguous subset of the plurality of WDM channels; and passing, by thesecond node on the first access ring network, the first discrete channelto a first customer location.
 17. The method of claim 16, furthercomprising: receiving, at a third node on the metro ring network, anoptical signal comprising the plurality of WDM channels minus the firstcontiguous subset of the plurality of WDM channels; filtering, by asecond passive, banded filter in the third node on the metro ringnetwork, a second contiguous subset of the plurality of WDM channels,wherein the second contiguous subset is different than the firstcontiguous subset; passing, by the third node on the metro ring network,the second contiguous subset of the plurality of WDM channels to asecond access ring network; receiving the second contiguous subset ofthe plurality of WDM channels at a fourth node on the second access ringnetwork; filtering, by a second tunable filter in the fourth node on thesecond access ring network, a discrete channel from the secondcontiguous subset of the plurality of WDM channels; and passing, by thefourth node on the second access ring network, the discrete channel fromthe second contiguous subset of the plurality of WDM channels to asecond customer location.